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Systematics and Evolution of Early Eocene Hyaenodontidae (Mammalia, Creodonta) in the Clarks Fork Basin, Wyoming
Abstract
327-391 http://deepblue.lib.umich.edu/bitstream/2027.42/48535/2/ID388.pdf
We describe three new hyaenodonts from the late Ypresian locality of Prémontré (Aisne, France; close to MP 10 reference level). The new species – Lesmesodon gunnelli nov. sp., Cynohyaenodon smithae nov. sp., and Eurotherium mapplethorpei nov. sp. – represent the oldest occurrences of these three European genera. Lesmesodon gunnelli is also reported from the locality of Cuis (Marne, France; Ypresian, ∼MP 10). We further present the dentition of two specimens of Lesmesodon edingeri from Messel (Hessia, Germany; type locality of the genus) based on µCT scans. Cynohyaenodon smithae and Lesmesodon gunnelli support the presence of small (300-400 g) hyaenodonts in the late Ypresian of the Paris Basin. Estimates of dental indices indicate that these hyaenodonts had an insectivorous diet. The third species – referred to Eurotherium – may have weighed 4-5 kg and, based on dental indices, likely incorporated more vertebrate prey into its diet. We also performed a phylogenetic analysis in order to test the relationships of these new taxa. These newly discovered species imply that the Proviverra/Allopterodon, Cynohyaenodon, and Eurotherium clades appeared in Europe earlier than previously known (i.e., Lutetian, MP 11). They reinforce the hypothesis that the hyaenodonts radiated during the middle-late Ypresian (MP 8/9-10) in Europe and adapted at that time to diverse ecological niches that they still occupied in the Priabonian (MP 13-14).
The middle Eocene Washakie Formation of Wyoming, USA, provides a rare window, within a single depositional basin, into the faunal transition that followed the early Eocene warming events. Based on extensive examination, we report a minimum of 27 species of carnivorous mammals from this formation, more than doubling the previous taxic count. Included in this revised list are a new species of carnivoraform, Neovulpavus mccarrolli n. sp., and up to ten other possibly new taxa. Our cladistic analysis of early Carnivoraformes incorporating new data clarified the array of middle Eocene taxa that are closely related to crown-group Carnivora. These anatomically relatively derived carnivoraforms collectively had an intercontinental distribution in North America and east Asia, exhibiting notable variations in body size and dental adaptation. This time period also saw parallel trends of increase in body size and dental sectoriality in distantly related lineages of carnivores spanning a wide range of body sizes. A new, model-based Bayesian analysis of diversity dynamics accounting for imperfect detection revealed a high probability of substantial loss of carnivore species between the late Bridgerian and early Uintan North American Land Mammal ‘Ages’, coinciding with the disappearance of formerly common mammals such as hyopsodontids and adapiform primates. Concomitant with this decline in carnivore diversity, the Washakie vertebrate fauna underwent significant disintegration, as measured by patterns of coordinated detection of taxa at the locality level. These observations are consistent with a major biomic transition in the region in response to climatically induced opening-up of forested habitats.
UUID: http://zoobank.org/9162f1a6-a12c-4d55-ba1d-dc66e8cda261
The carnivorous mammalian fauna from the Uintan (late middle Eocene) of North America remains relatively poorly documented. This is unfortunate, as this is a critical interval in the transition from “creodont” to carnivoran dominated carnivore guilds. This study reports a new species from the Uinta Formation of the Uinta Basin, Utah, the first North American species of the otherwise Asian hyaenodont genus Propterodon . The new species, Propterodon witteri , represented by a dentary with M 2-3 from the late Uintan Leota Quarry, is larger than the well-known P. morrisi and P. tongi and has a larger M 3 talonid, but is otherwise very similar. A phylogenetic analysis of hyaenodont interrelationships recovers P. witteri as a hyaenodontine but is generally poorly resolved. A relationship between Hyaenodontinae and Oxyaenoides , recovered by many recent analyses, is not supported. Among the Asian species of Propterodon , P. pishigouensis is reidentified as a machaeroidine oxyaenid and recombined as Apataelurus pishigouensis new combination. Isphanatherium ferganensis may also represent an Asian machaeroidine. Identification of a North American species of Propterodon and an Asian Apataelurus increases the similarity of North American Uintan and Asian Irdinmanhan faunas and suggests that there was substantial exchange of carnivorous fauna during the late middle Eocene.
The middle Eocene Pondaung Formation in Myanmar has yielded a rich mammalian fauna including several Primate taxa. Hyaenodonta are known by the genera Kyawdawia, Yarshea, Orienspterodon, and two other indeterminate taxa. We describe here new material of Kyawdawia, including some morphological details, a new species of the hypercarnivorous genus Propterodon and an indeterminate species, different from those described earlier in Myanmar, and characterized by a reduction of m3 and would belong to a third lineage with the same evolutionary trend as Galecyon and the Limnocyoninae. The hyainailourines (Orienspterodon) and hyaenodontines (Propterodon) are recorded for the first time in Southeast Asia and these subfamilies appeared in quasi the same time in Europe illustrating probably a profound change in the carnivorous fauna among Laurasia.
Supplementary Information.
Supplementary Tables S1 and S2; Supplementary Figures S1?S5; and Supplementary References.
The 'Age of Mammals' began in the Paleocene epoch, the 10million year interval immediately following the Cretaceous-Palaeogene mass extinction. The apparently rapid shift in mammalian ecomorphs from small, largely insectivorous forms to many small-to-large-bodied, diverse taxa has driven a hypothesis that the end-Cretaceous heralded an adaptive radiation in placental mammal evolution. However, the affinities of most Paleocene mammals have remained unresolved, despite significant advances in understanding the relationships of the extant orders, hindering efforts to reconstruct robustly the origin and early evolution of placental mammals. Here we present the largest cladistic analysis of Paleocene placentals to date, from a data matrix including 177 taxa (130 of which are Palaeogene) and 680 morphological characters. We improve the resolution of the relationships of several enigmatic Paleocene clades, including families of 'condylarths'. Protungulatum is resolved as a stem eutherian, meaning that no crown-placental mammal unambiguously pre-dates the Cretaceous-Palaeogene boundary. Our results support an Atlantogenata-Boreoeutheria split at the root of crown Placentalia, the presence of phenacodontids as closest relatives of Perissodactyla, the validity of Euungulata, and the placement of Arctocyonidae close to Carnivora. Periptychidae and Pantodonta are resolved as sister taxa, Leptictida and Cimolestidae are found to be stem eutherians, and Hyopsodontidae is highly polyphyletic. The inclusion of Paleocene taxa in a placental phylogeny alters interpretations of relationships and key events in mammalian evolutionary history. Paleocene mammals are an essential source of data for understanding fully the biotic dynamics associated with the end-Cretaceous mass extinction. The relationships presented here mark a critical first step towards accurate reconstruction of this important interval in the evolution of the modern fauna. Biological Reviews
The ringtail (Bassariscus astutus) is a widely distributed small carnivorous mammal (Procyonidae) in Mexico and the southwestern United States. As in other procyonids, the ringtail is capable of rotating its hind foot to allow headfirst descent of vertical substrates. The osteological correlates of this process, termed hind foot reversal, are well documented, but potential myological correlates have never been investigated. We present the 1st detailed study of the muscular anatomy of the hind limb of B. astutus, including the 1st muscle maps of the pelvis and pes of any procyonid. Comparison of the hind limb myology of the ringtail with other arctoid carnivorans, including taxa incapable of hind foot reversal, indicates that the muscles responsible for the action of reversal do not differ significantly between nonreversing forms and taxa capable of partial or full reversal. This suggests that specific myological adaptations are not necessary to achieve hind foot reversal. However, increased development of the digital flexors, which maintain a grip while body mass is supported by the hind limb, may characterize taxa that make use of reversed postures. The hind limb myology of members of Procyonidae does not strongly support either morphological or molecular hypotheses of relationship, in part because relatively few differences among members of the family can be documented.
The proviverrines from the Ypresian (MP7–MP10) and Lutetian (MP11–MP14) are represented mainly by species recorded in the northern and central parts of Europe (Paris Basin, Belgian Basin, Germany, Switzerland). Here, we describe fossils from southern France: Saint-Papoul (MP8 + 9; Aude) and Aigues-Vives 2 (?MP13; Aude). One dentary with secant molars from Saint-Papoul represents a new genus and species, Preregidens langebadrae. This taxon is possibly present in Avenay (France), the MP8 + 9 reference locality. One of the three dentaries discovered in Aigues-Vives 2 belongs to the hypercarnivorous Oxyaenoides schlosseri, previously represented by only two isolated lower molars. This dentary appears to be the most derived of the proviverrines. This species is possibly present in Saint-Martin-de-Londres (France), a locality that is considered to be close to the MP13 reference level. The two other dentaries from Aigues-Vives 2 support the presence of Eurotherium theriodis and provide the first possible evidence of sexual dimorphism in a proviverrine species. A phylogenetic analysis of the proviverrines is performed to resolve the phylogenetic position of the three taxa. This identifies a close relationship between the new genus (Preregidens) and Oxyaenoides. The new fossils allow the age of Saint-Papoul and Aigues-Vives 2 to be refined: the first locality is considered to be close in age to Avenay (Ypresian; France), while the second one seems to be close to Egerkingen γ (Lutetian; Switzerland), which is considered to be possibly close in age to the MP13 reference level. Finally, the presence of O. schlosseri and E. theriodis in the southern part of France is compatible with the hypothesis that the mammals involved in the first intra-Eocene turnover migrated northwards.
New remains of the early Eocene hyaenodontid Indohyaenodon raoi are described from the Vastan Lignite Mine in Gujarat, western India, including the first known rostrum, upper dentition, and postcrania, substantially expanding our knowledge of the species and providing insights into its functional morphology and relationships. Craniodental morphology suggests that I. raoi had a broad diet, including non-vertebrate material as well as flesh of a diversity of prey species. Postcranial morphology is broadly similar to that of other early hyaenodontids and suggests a scansorial locomotor repertoire. Dental morphology indicates that I. raoi is closely related to other South Asian hyaenodontids, with shared features including strong cingula, narrow premolars, and a reduced P4 protocone. We present the most comprehensive phylogenetic analysis of Hyaenodontidae to date, which corroborates this relationship but finds South Asian hyaenodontids to be the stem of a group that includes most African hyaenodontids. This and other higher-level relationships within Hyaenodontidae are, however, weakly supported, and substantially different alternative hypotheses of relationships are not significantly less parsimonious, reflecting strong character conflict. Factors contributing to this conflict include the isolation of hyaenodontid faunas on different continents during much of the Eocene, canalization and simplification of carnivorous dentitions, and a lack of non-dental material for critical hyaenodontid groups. The new phylogeny is consistent with either an African or an Asian origin for the group.
Here we describe and illustrate specimens of hyaenodont mammals from two Early Eocene localities of Southern France: Fournes (Minervois) and Fordones (Corbières). Some of these specimens were previously described as cf. Hyracolestes sp. (Cimolesta, Sarcodontidae), a taxon only known from Asia, but new arguments allow their referring to the small proviverrine hyaenodont Parvagula palulae which was previously only recorded in Palette (Provence). The material notably includes the oldest p4 ever recorded for the European endemic subfamily Proviverrinae. This new material shows that, by the beginning of the Early Eocene, proviverrines already display their typical combination of dental features characterized by the presence of a large paraconid and entoconid on p4. The comparison between the earliest European proviverrines and sinopines (a mostly North American radiation) supports the divergence of the two subfamilies by this time. Moreover, the early proviverrines are morphologically similar to the African hyaenodont Tinerhodon (Late Paleocene). Consequently, the history of the European proviverrines is likely rooted in Africa. Finally, the new specimens support a similar age for the localities of Palette and Fordones, and a younger age for Fournes. Due to the ages of these localities Parvagula palulae must be regarded as the oldest proviverrine.
A new genus and species of carnivorous mammal is described from early Eocene (Wasatchian) sediments of the Clark's Fork and Bighorn Basins in northwestern Wyoming. The new form has cheek teeth most closely resembling those of Asian Didymoconidae; however, it retains a full complement of four premolars and three molars. A new subfamily is proposed for primitive generalized didymoconids including the Wyoming genus and, tentatively, Mongoloryctes. Didymoconines Archaeoryctes, Hunanictis, Ardynictis, and Didymoconus, ranging from the late Paleocene to Oligocene in Central Asia, represent a radiation characterized by loss of P11 and M33 with progressive simplification of the remaining cheek teeth. The Wyoming didymoconid is known only from early Wasatchian faunas. This restricted temporal distribution, together with its systematic affinities, suggests that the Wyoming form was a short-lived North American immigrant representing a group whose principal radiation occurred in Asia. The Wyoming form is one of the oldest and most primitive didymoconids. Among Paleocene mammals it most closely resembles Yantanglestes conexus, an early mesonychid from the middle(?) Paleocene of South China, suggesting that didymoconids and mesonychids may share a common ancestry. Didymoconidae are provisionally classified with Mesonychidae in the order Condylarthra.
The action of carnassial dentitions in placentals and marsupials is discussed and related to their growth, structure, and evolution. The larger prey relative to their own body size of larger carnivores accounts for the major dental differences between carnivores and insectivores. Graphic comparisons relate length and angle of the shear on different teeth, and tooth position, to phylogeny; the graphs can be interpreted both functionally and developmentally. Convergence in form and function sometimes is, and sometimes is not, accompanied by a convergence in growth fields.
Second account of the new Vertebrata from the Bridger Eocene
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Eocine Siugethiere aus dem Gebiet des schweizerischen Jura. Neue Denkschriften der Allgemeinen schweizerischen Gesellschaft fiir die gesammten
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